The ability of Acidithiobacillus ferrooxidans to remove chromium and other metals from LD slag was examined. Additionally the option to retrieve P from LD slag was evaluated. Due to the facts that A. ferrooxidans is a facultative anaerobic microorganism and LD slag is an alkaline and oxidic material, both oxidative and reductive bioleaching experiments were carried out. In the reductive mode, four different gas atmospheres (nitrogen, carbon dioxide, air and a mixture of N2 and CO2) were considered. Promising results were obtained by reductive bioleaching with A. ferrooxidans and a pure carbon dioxide atmosphere, 83 % chromium could be removed. In comparison, only 27 % Cr were removed by oxidative bioleaching. The degree of P removal could not be easily determined due to imbalanced data obtained.